More Than Machines: Physics & Free Will

Article excerpt

"What is man, that thou art mindful of him? And the son of man, that thou visitest him?" So asked the psalmist three thousand years ago. The question is still with us and as urgent as ever: What are we? The scriptural answer is that we are made in the image of God, but that answer is not as plausible to many people today as it once was. Reductive theories abound that claim human beings are nothing more than the product of biological and social evolution, of genes and the environment, of instincts and social conditioning, of the wiring of the brain and the chemistry of hormones and neurotransmitters. What gets lost in all this is free will.

Explaining how man is made in the image of God, the second-century theologian St. Irenaeus of Lyons wrote that "man is rational and therefore like God; he is created with free will and is master over his acts." This freedom is what makes us persons, and it is what allows us to share in the divine life. To share in that life, says St. John the Evangelist, is to abide in love and in truth; and that is only possible for us to do because we are endowed with freedom. If we were entirely controlled by factors of a lower order, by mere material forces, as animals are, we could not be open to realities of a higher order, to goodness, truth, and beauty. According to the Catechism of the Catholic Church, in "his openness to truth and beauty, his sense of moral goodness, his freedom and the voice of his conscience," man finds evidence "of his spiritual soul," which is "irreducible to the merely material."

The belief that human beings have spiritual (or nonphysical) souls and are thereby endowed with free will has been under attack for a long time by philosophers, scientists, and even some theologians. The basis of that attack is a philosophical idea called "physicalism," which maintains that human beings are completely explicable in material terms: we are, say physicalists, nothing but enormously complicated biochemical machines.

This idea has deep historical roots. The predictable motions of the heavenly bodies led very early to the idea that the astronomical universe is a clocklike mechanism--already a commonplace among medieval thinkers. In the seventeenth century, as it became clear that terrestrial phenomena, like celestial ones, are governed by precise mathematical laws, the idea began to emerge that plants, animals, and even the human body can also be understood as machines. That was the view of both Descartes and Pascal, though they drew the line at the human soul, whose immateriality they continued to affirm. The more radical thinkers of the Enlightenment, including Hobbes, La Mettrie, and Baron D'Holbach, went further. They denied the spiritual soul and its freedom and asserted that man in his entirety is mechanical--hence the title of La Mettrie's famous work, L'Homme machine.

Such thoroughgoing physicalism was still unusual in the eighteenth century, even among the philosophes, but it has gained enormous traction in our own day. As computer technology has advanced, even ordinary people have become accustomed to the idea, popularized by science fiction, that artificial machines might eventually become as conscious and intelligent as we are. This is the natural corollary of the idea that we ourselves are just "machines made of meat," in the famous words of Marvin Minsky, a pioneer in artificial-intelligence research.

Many factors have contributed to this development. The defeat of vitalism in the nineteenth century promised that the same reductionist modes of explanation that had been so successful in physics would unlock the secrets of biology as well--as indeed they have, to a remarkable degree. By showing the continuities that exist between ourselves and the lower animals, Darwin's discoveries weakened belief in human exceptionalism. But a decisive shift had already occurred much earlier, with the discoveries of Isaac Newton, whose laws of gravity and mechanics had two profound features. …